15 Life Lessons You Should Learn Before Entering Your 20s

I look back now, though, and I realize I'm less than a year away from turning 20. I'm less than a year away from being on this planet for two whole decades.

Surprisingly, I've garnered more wisdom in these short years than I ever thought I would.

Here are 15 life lessons I've learned that I think everyone should know by their 20s:

People grow apart.

Chances are that you'll probably only stay in touch with a few of the friends you swore you'd always hold close.

As you get older, you meet new people, your priorities change and you might only message a yearly "happy birthday" to some of your closest friends from childhood.

Heartbreak is inevitable.

As tempting as living life completely emotionless may seem sometimes, none of us are immune to feelings and heartbreak. There's a chance you'll experience your fair share of heartbreak, maybe even more than once. Just remember that you're also strong enough to move past it.

People are not irreplaceable.

Aside from your immediate family members, almost every person in your life can be replaced. Remember that boyfriend you cried over incessantly? With a little patience, you'll probably find someone even better.

People die.

As children, we're typically not as attune to the deaths occurring around us, but as we age, it becomes a sad part of our lives.

You'll hear more about deaths on the news. Family members and friends might pass away. Unfortunately, the worst part is that there's often nothing we can do about it. Death is the only thing in life that's certain, and all we can do is learn to deal with it.

You have to work hard to get what you want.

On "Gossip Girl," Blair Waldorf once said, "Destiny is for losers. It's just a stupid excuse to wait for things to happen instead of making them happen."

Nothing will be handed to you. You have to go out there, approach the real world and take what you want.

Don't be a pushover.

Helping others every now and then is a good thing, but letting people take advantage of you isn't. If you let people step all over you, then you'll be the only one hurting in the long run. Don't let that happen.

Sleep is important.

As children, we do everything in our power to stay up as late as possible. The truth, however, is that sleep is a valuable and necessary asset. When you start pulling all-nighters and relying on power naps, a 9 pm bedtime seems like a dream.

Health is wealth.

Yes, it's a cliched saying, but when we're younger, we tend to treat our bodies terribly. From junk food to alcohol to lack of exercise, we think that nothing will affect us.

On the contrary, you could have all the money in the world, and it still wouldn't be as valuable as your physical and mental health.

It's OK to be selfish sometimes.

Learn to say "no." Don't ever do something that makes you uncomfortable. Always put yourself first. If you don't, then who's going to?

Your friend circle might shrink as you age.

In elementary school, every person around you is your friend. Then, in middle school and high school, you probably had a huge clique that you thought would stick together forever. As you get older, though, you find yourself close to fewer and fewer people.

You have more insight as to what you're looking for in your relationships, and you only keep the most fulfilling ones close.

Not everyone is your fan.

There's bound to be at least one person who doesn't like you very much.

You can't please everyone, because it's simply not possible. It may be hard to accept that not every person you meet will be an admirer, but that's OK. Chances are that you're not a fan of every person you meet either.

Education matters.

It's easy to slack off in school as a kid and still manage to get by with decent grades. However, in college especially, you quickly realize that quality education requires hard work.

The world can be cruel.

We grow up idolizing fantastical fairytales and "happy ever afters," but in reality, they're just that: fairytales.

Whether it's in your personal life or on a global scale, bad things happen all the time. Accept them as they come, and try not to lose sight of the good in the world.

Having people you can rely on is important.

There are few things more valuable than having people you know will always be by your side. If there are people in your life who are there for you emotionally, physically or morally, cherish them and never let them go.

Live life to the fullest.

While most of the other things on this list might seem pessimistic, just remember that life is short. Travel, meet new people, do what makes you happy and make the most of your life.

Always learn from the things you've done wrong so you don't repeat the same mistakes again.